let watermark = {};

let setWatermark = (str) => {
  let id = "1.23452384164.123412415";

  if (document.getElementById(id) !== null) {
    document.body.removeChild(document.getElementById(id));
  }

  let can = document.createElement("canvas");
  can.width = 160;
  can.height = 100;

  let cans = can.getContext("2d");
  cans.rotate((-20 * Math.PI) / 120);
  cans.font = "12px Vedana";
  cans.fillStyle = "rgba(0,0,0,1)";
  cans.textAlign = "left";
  cans.textBaseline = "Middle";
  cans.fillText(str, can.width / 20, can.height);

  let div = document.createElement("div");
  div.id = id;
  div.style.pointerEvents = "none";
  div.style.top = "3px";
  div.style.left = "0px";
  div.style.position = "fixed";
  div.style.zIndex = "100000";
  div.style.width = document.documentElement.clientWidth * 2 + "px";
  div.style.height = document.documentElement.clientHeight * 2 + "px";
  div.style.opacity = "0.15";
  div.style.background =
    "url(" + can.toDataURL("image/png") + ") left top repeat";
  document.body.appendChild(div);
  return id;
};

// 该方法只允许调用一次
watermark.set = (str) => {
  setWatermark(str);
};

watermark.clear = () => {
  let id = "1.23452384164.123412415";
  if (document.getElementById(id) !== null) {
    document.body.removeChild(document.getElementById(id));
  }
};

export default watermark;
